THE GENERAL COMPOSITION OF MILK 



The heat value of the food taken can only be ascertained approxi- 

 mately, owing to the difficulty of obtaining all the colostrum 

 except by suckling, and to the fact that the colostrum cannot be 

 used both for estimation and as a food for the infant. 



Langstein, Rott, and Edelstein endeavoured to avoid some of 

 these difficulties by expressing some milk before and after feeding, 

 and mixing the samples thus obtained. If the total amount of 

 milk available is known and the heat value of an average sample 

 is ascertained, a reasonable approximation may be arrived at as 

 to the calories available for the infant. 



Langstein and his colleagues took samples from eight cases, 

 and concluded that all colostrum did not have the same heat 

 value. They divided the results obtained into two classes, of 

 which the hea.t value per litre of milk for Group I. (of rich colostrum) 

 is given as : 



Day 



I 

 2 

 3 



4 

 5 

 6 



7 



Calories per Litre. 



1480 



. Il8o 

 8lO 

 730 

 7OO 



675 

 650 



In Group II. (poor colostrum) there was little difference in 

 caloric value as compared with that of the later days. 



Birk studied the metabolism of two children, one of whom 

 was fed naturally from birth, with colostrum passing to later 

 milk, while the other received no colostrum, but was fed by a 

 wet-nurse in a later stage of lactation. Although the first child 

 lost weight in the usual way, it showed a . positive balance for 

 nitrogen and salts ; the other child showed a negative balance for 

 nitrogen and several saline constituents, viz. : 



The percentage retention of the salts is interesting, and the 



C 2 



